General operating mode

General operation

The air conditioning function is divided into four sub-functions: heating, refrigerant loop, cabin ventilation and user selection. Diagnosis of the air conditioning, using the diagnostic tool, is carried out in two ways.

The first way is module diagnosis, which allows communication with a single control module (select the module concerned). The second way is function diagnosis, which allows communication with the four control modules of the AIR CONDITIONING function.

Description of the sub-functions

Heating sub-function: this sub-function includes everything used to produce the vehicle's warm air and to manage the rear window defroster.

The main control modules concerned are the air conditioning control module (air mixing and blown air setpoint) and the Cabin Central Unit (management and control of the cabin heating resistors). The Protection and Switching Unit controls the rear window defroster (and mirror defrosting). The injection control module is only present in this sub-function to provide the information required for its management.

Refrigerant loop sub-function: this sub-function includes everything used to produce the vehicle's cold air.

The control modules concerned are air conditioning for air mixing, injection for authorising compressor engagement, and the Protection and Switching Unit for controlling the compressor and the engine fan assemblies. For automatic climate control, the Cabin Central Unit only transmits the compressor engagement request from the air conditioning control module to the injection control module.

For manual air conditioning, the Cabin Central Unit authorises or not the sending of the compressor engagement request from the air conditioning control module to the injection control module depending on the state of the cabin blower (in manual air conditioning, the Cabin Central Unit receives and manages the cabin blower speed information: the prohibition is given if it is not operating).

User selection sub-function: this sub-function includes everything used to translate the user's request (button presses). The control modules concerned are the air conditioning control module for automatic climate control and the Central Unit. The other two control modules are not concerned for manual air conditioning.

Cabin ventilation sub-function (automatic climate control only): this sub-function includes everything relating to ventilation, air mixing, air recirculation and air distribution. Only the air conditioning control module is therefore concerned.

Exchanges between the four control modules of the air conditioning function

• air conditioning request 1 (compressor engagement)
• cabin heating resistor (RCH) engagement request
• rear window defroster engagement request (+ electric mirrors)
• cabin ventilation information

• cabin heating resistors (RCH) operation freeze
• outside temperature information
• engine coolant temperature information
• rear window defroster engagement request (+ electric mirrors)

• alternator load information
• number of cabin heating resistors authorised by alternator
• air conditioning request 2 (compressor engagement)
• fast idle request for cabin heating resistors (RCH)

• compressor engagement authorisation
• engine coolant temperature information
• refrigerant fluid pressure information
• number of cabin heating resistors authorised by injection
• compressor engagement request
• engine cooling fan assembly engagement request

• alternator load information

Summary of elements controlled or managed by the automatic climate control unit

Summary of elements controlled or managed by the manual climate control unit

Summary of elements controlled or managed by the control panel on heating-only versions (without air conditioning)

Summary of elements controlled or managed by the Passenger Compartment Central Unit

Summary of elements controlled or managed by the injection ECU

Block diagram of the compressor control